Wisconsin's attorney general on Thursday appealed a federal judge's ruling from last month striking down the state's ban on same-sex marriages as unconstitutional.

U.S. District Judge Barbara Crabb ruled on June 6 that the ban, approved by voters in 2006, was a violation of gay couples' equal protection and due process rights. More than 500 same-sex couples got married in the state before Crabb put her ruling on hold a week later, pending the expected appeal from Republican Attorney General J.B. Van Hollen.

The case now heads to the 7th U.S. Circuit Court of Appeals in Chicago.

The lawsuit was brought by the American Civil Liberties Union on behalf of eight same-sex couples. Last week it asked Crabb to lift her stay of the ruling, which would allow the marriages to resume. Crabb has not ruled on that request.

John Knight, an ACLU attorney, did not immediately respond to an email seeking comment.

The 7th Circuit last month ordered an expedited schedule in Indiana's case, requiring parties to file all of their briefs on motions no later than Aug. 5, with oral arguments to be scheduled a short time later.

Van Hollen had until July 21 to file an appeal, but he said in a statement that the appeals court's decision to speed up the Indiana case led him to do it sooner.

"The goal of our timing is simple: to ensure that Wisconsin is placed on equal footing with Indiana, and that our constitution and laws are given timely consideration by the appellate judges," Van Hollen said in an email.

Republican Gov. Scott Walker, who is seeking re-election this year and considering a run for president in 2016, was an early vocal supporter of the gay marriage ban and voted for it in 2006. But amid polls showing most Wisconsin voters support gay marriage, Walker has said his position doesn't matter because the governor plays no role in changing the constitution.

Walker is a named defendant in the lawsuit and has been supportive of Van Hollen appealing the ruling. Walker's spokeswoman Laurel Patrick did not immediately return an email seeking comment.

Wisconsin's constitutional amendment was approved by 59 percent of voters in 2006. It outlawed gay marriage or anything substantially similar. The ACLU said the ban violated the constitutional rights of eight gay couples to equal protection and due process and Crabb agreed.

The victory was the 15th straight win for gay rights activists since a landmark Supreme Court ruling last summer striking down part of the federal Defense of Marriage Act. That ruling allowed married same-sex couples to receive the same federal benefits as other married people, but did not specifically address whether gay marriage is a constitutional right.

The Supreme Court is expected to take up the issue when it returns to work in October. On Wednesday, Utah's attorney general decided to bypass a full appeals court and take its case straight to the Supreme Court.

The high court is under no obligation to the take the case, and it could wait for rulings from one or more of the five other appellate courts with gay marriage cases pending.

Lower courts have repeatedly cited the Supreme Court's decision from last year when striking down gay marriage bans. The latest such ruling was Wednesday, when a state judge struck down Colorado's gay marriage ban. That ruling is on hold pending an appeal.

In addition to Wisconsin, judges have ruled against bans in Arkansas, Idaho, Michigan, New Mexico, Oklahoma, Oregon, Pennsylvania, Texas, Utah, Virginia, Indiana and Colorado. They have ordered Kentucky, Indiana, Ohio and Tennessee to recognize same-sex marriages from other states.